The present invention relates to the use of tertiary amino alkyl amides as catalysts for producing polyurethane foams.
The present invention relates to tertiary amino alkyl amide catalysts for producing polyurethane foams. Polyurethane foams are widely known and used in automotive, housing and other industries. Such foams are produced by reaction of a polyisocyanate with a polyol in the presence of various additives. One such additive is a chlorofluoro-carbon (CFC) blowing agent that vaporizes as a result of the reaction exotherm causing the polymerizing mass to form a foam. The discovery that CFCs deplete ozone in the stratosphere has resulted in mandates diminishing CFC use. Production of water blown foams, in which blowing is performed with carbon dioxide (CO2) generated by the reaction of water with the polyisocyanate, has therefore become increasingly important. Tertiary amine catalysts are typically used to accelerate blowing (reaction of water with polyisocyanate to generate CO2) and gelling (reaction of polyol with isocyanate).
The ability of the tertiary amine catalyst to selectively promote either blowing or gelling is an important consideration in selecting a catalyst for the production of a particular polyurethane foam. If a catalyst promotes the blowing reaction to a too high degree, much of the CO2 will be evolved before sufficient reaction of isocyanate with polyol has occurred, and the CO2 will bubble out of the formulation, resulting in collapse of the foam. A foam of poor quality will be produced. In contrast, if a catalyst too strongly promotes the gelling reaction, a substantial portion of the CO2 will be evolved after a significant degree of polymerization has occurred. Again, a poor quality foam will be produced, this time characterized by high density, broken or poorly defined cells, and other undesirable features.
Tertiary amine catalysts generally are malodorous and offensive and many have high volatility due to their low molecular weight. Release of the tertiary amine during the foam processing may present significant safety and toxicity problems, and release of residual amine from customer products is generally undesirable.
Amine catalysts which contain amide functionality derived from carboxylic acids with long chain alkyl groups (C6 or higher) and fatty acids have an increased molecular weight and hydrogen bonding ability and reduced volatility and odor when compared with related structures which lack this functionality. Furthermore, catalysts which contain amide functionality chemically bond into the polyurethane polymer during the reaction and are not released from the finished product. Catalyst structures that embody this concept are typically of low to moderate activity and promote both the blowing (water-isocyanate) and the gelling (polyol-isocyanate) reactions to varying extents.
U.S. Pat. No. 4,242,467 discloses the use of morpholino and piperazino substituted ureas as catalysts for producing polyurethane foams.
U.S. Pat. No. 4,644,017 discloses the use of certain diffusion stable amino alkyl ureas having tertiary amino groups in the production of a polyisocyanate addition product that does not discolor or change the constitution of surrounding materials. Specifically taught are Catalyst A and Catalyst D which are reaction products of dimethylamino-propylamine and urea.
U.S. Pat. No. 4,007,140 discloses the use of N,N′-bis(3-dimethylaminopropyl)urea as a low odor catalyst for the production of polyurethanes. The use of N-(3-dimethylaminopropyl)-formamide is also described as a catalyst to make polyurethane foams.
U.S. Pat. No. 4,012,445 discloses the use of beta-amino carbonyl compounds as catalysts for the production of polyurethane foams. In these catalysts, the beta-amino part is present as a dialkylamino or a N-morpholino or a N,N′-piperazino heterocyclic nucleus and the carbonyl part is present as an amido or ester group.
U.S. Pat. No. 4,735,970 discloses a process for the production of cellular polyurethanes using special amine-CO2 adducts and homogeneous mixtures of these adducts. The use of N-(3-dimethylaminopropyl)-formamide is also described as a catalyst to make polyurethane foams.
U.S. Pat. No. 5,200,434 discloses the use of amide derivatives of alkylene oxide polyethers and their uses in polyurethane foam formulation.
U.S. Pat. Nos. 5,302,303, 5,374,486, and 5,124,367 disclose the use of fatty amido amines as a component necessary for the stabilization of isocyanate compositions containing flame-retardants. The shelf-life stability of isocyanate-reactive compositions is often adversely affected by the addition of flame-retardants, especially those based on phosphorous, zinc, antimony, and aluminum. The use of fatty amino amides improves the storage stability of these isocyanate mixtures.